Solid state lighting technology is beginning to penetrate the white lighting market due to recent gains in LED device and luminaire efficacy. LED solutions can be found in applications where LEDs can be distributed to ease the difficulty of thermal management, such as linear strips and down-lighting solutions where the luminaire is relatively large. Development of small form factor LED retrofits with high luminous flux has been challenging because of the limited volume for driver electronics and surface area for heat dissipation.
Conventional 50 W Sylvania MR16 halogen reflector lamps, such as shown in FIG. 1, are small form factor lamps primarily used in interior retail and residential applications. Dimensions of the MR16 are no more than about 2.0 inches in diameter and 1.9 inches in overall length. A 50 W halogen achieves about 600 lumens. Beam angle varies by application, ranging from less than 10° narrow spot lights to about 60° wide flood lights. Color quality is important in retail applications as the light output from the lamps must render merchandise in a very high quality.
Typically, the most efficacious high CRI warm white approach is to mix white phosphor converted InGaN LEDs with red InGaAlP LEDs. Since the two materials have different thermal characteristics, a complex and costly sensing and feedback control mechanism is needed to stabilize the white color point. This technique is not suitable for the small MR16 lamp; there simply is not sufficient space to house both LED drivers and control systems and such a replacement lamp may not have sufficient heat sinking area to maintain low InGaAlP junction temperatures required for this technique.